Laminated glass having the function of shielding heat rays, ultraviolet rays, or the like is formed such that film layers for shielding heat rays, ultraviolet rays, or the like are respectively formed on respective one surface of two glass plates by sputtering (metallic deposition) and are inwardly opposed to each other, and pressure, heat, and the like are applied to the two glass plates with a polyvinyl butyral sheet placed therebetween, thereby bonding the film layers and the polyvinyl butyral sheet. However, since the film layers and the polyvinyl butyral sheet are difficult to bond to each other, the state of their bonding is likely to become incomplete, and moisture, air, and the like can possibly enter peripheral portions of the laminated glass where the state of bonding is incomplete. Consequently, the polyvinyl butyral sheet becomes oxidized and undergoes color development and change. Accordingly, the film layers at the peripheral portions are removed, and the glass plates and the polyvinyl butyral sheet, which are easily bonded to each other, are bonded to each other.
Meanwhile, double glazing having the function of shielding heat rays, ultraviolet rays, or the like is formed such that film layers are respectively formed on respective one surface of two glass plates and are inwardly opposed to each other, and in order to obtain a hermetically sealed state between them, spacers are inserted between and bonded to the two glass plates at their peripheral portions by means of a pressure-sensitive adhesive elastic material (hereafter referred to as butyl rubber) formed of butyl and Thiokol. However, since the film layers and the butyl rubber are difficult to bond to each other, the state of their bonding is likely to become incomplete, and moisture and the like can possibly enter those portions where the state of bonding is incomplete, making it impossible to maintain the hermetically sealed state. Consequently, the heat insulating effect deteriorates appreciably, and water droplets and the like can occur on the film layers. Therefore, the film layers at the peripheral portions are removed, and the glass plates and the butyl rubber, which are easily bonded to each other, are bonded to each other.
Incidentally, in a case where the film layer is ground and removed by bringing a grinding wheel into contact with the film layer at the peripheral portions of the glass plate by means of resiliency and by rotating this grinding wheel and moving the grinding wheel itself, if an attempt is made to remove the film layer reliably up to an edge portion of the glass plate, it is inevitable to move the grinding wheel up until it has passed the edge portion of the glass plate. However, if the grinding wheel passes the edge portion of the glass plate, the grinding wheel is lowered by the resiliency with which the grinding wheel is resiliently urged, and the grinding wheel is brought into contact with a glass-plate placing surface on which the glass plate is placed. Hence, there is a possibility that the placing surface is undesirably ground unnecessarily.
Such a drawback occurs not only in the apparatus for removing a film layer on a glass plate for removing a film layer formed on one surface of the glass plate, but also in the apparatus for forming a cut line on a glass plate for forming a cut line for bend-breaking on one surface of the glass plate. For example, in the cut-line forming apparatus, a cutter wheel for forming a cut line is brought into contact with the glass-plate placing surface on which the glass plate is placed, and there is a possibility that a cut line is undesirably formed unnecessarily on the glass-plate placing surface.
In addition, the grinding wheel becomes gradually worn due to the grinding of the film layer with respect to the glass plate, and its diameter becomes small. However, if the diameter of the grinding wheel becomes small, the pressing force of the grinding wheel against the glass plate on the basis of the resiliency becomes small, with the result that there is a possibility that the removal of the film layer by the grinding wheel fails to be effected as desired. Therefore, there is a drawback in that the grinding wheel must be replaced at an early stage.
The present invention has been devised in view of the above-described various aspects, and its object is to provide a glass-plate working apparatus which is capable of removing the film layer or forming the cut line reliably up to an edge portion of the glass plate without unnecessarily grinding or cutting the glass-plate placing surface.
Another object of the present invention is to provide a glass-plate working apparatus which makes it possible to set the pressing force of the grinding wheel against the glass plate to a desired value even if the diameter of the grinding wheel becomes small due to its wear, thereby making it possible to avoid a decline in the manufacturing efficiency which is ascribable to the operation of replacing the grinding wheel.